Known audio amplifiers include those in which amplifying units can be configured by a user to drive speakers. Since it is not known in advance how the user will ultimately connect the amplifying units, it can be difficult to know in advance how much current the power supply should be capable of handling.
It is possible to simply provide the power supply with components that can handle even the most taxing configurations. But such configurations are rarely encountered in practice. Therefore, it is economically wasteful to adopt such a solution.